CN110529154A - Prefabricated assembled space grid structure and its construction method for tunnel support - Google Patents

Prefabricated assembled space grid structure and its construction method for tunnel support Download PDF

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Publication number
CN110529154A
CN110529154A CN201910868684.XA CN201910868684A CN110529154A CN 110529154 A CN110529154 A CN 110529154A CN 201910868684 A CN201910868684 A CN 201910868684A CN 110529154 A CN110529154 A CN 110529154A
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China
Prior art keywords
tunnel
supporting structure
net rack
supporting
prefabricated
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Pending
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CN201910868684.XA
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Chinese (zh)
Inventor
雷升祥
张旭东
夏明锬
梅灿
彭星新
张志勇
杨旭
董云生
黄明利
宋远
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Beijing Jiaotong University
China Railway 11th Bureau Group Co Ltd
China Railway Fifth Survey and Design Institute Group Co Ltd
China Railway Construction Corp Ltd CRCC
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Beijing Jiaotong University
China Railway 11th Bureau Group Co Ltd
China Railway Fifth Survey and Design Institute Group Co Ltd
China Railway Construction Corp Ltd CRCC
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Priority to CN201910868684.XA priority Critical patent/CN110529154A/en
Publication of CN110529154A publication Critical patent/CN110529154A/en
Pending legal-status Critical Current

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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
    • E21D11/04—Lining with building materials
    • E21D11/08—Lining with building materials with preformed concrete slabs
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
    • E21D11/04—Lining with building materials
    • E21D11/08—Lining with building materials with preformed concrete slabs
    • E21D11/083—Methods or devices for joining adjacent concrete segments
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
    • E21D11/04—Lining with building materials
    • E21D11/10—Lining with building materials with concrete cast in situ; Shuttering also lost shutterings, e.g. made of blocks, of metal plates or other equipment adapted therefor
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D11/00—Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
    • E21D11/14—Lining predominantly with metal
    • E21D11/15—Plate linings; Laggings, i.e. linings designed for holding back formation material or for transmitting the load to main supporting members
    • E21D11/152—Laggings made of grids or nettings

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  • Engineering & Computer Science (AREA)
  • Mining & Mineral Resources (AREA)
  • Architecture (AREA)
  • Structural Engineering (AREA)
  • Civil Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Geology (AREA)
  • Lining And Supports For Tunnels (AREA)

Abstract

A kind of prefabricated assembled space grid structure and construction method for tunnel support provided by the invention.The prefabricated assembled space net rack supporting construction includes at least two blocks prefabricated rack support units, passes through connecting elements connection Formation cross-section closing supporting construction identical with supporting tunnel cross-section shape between rack support unit；When it is constructed, the interior force parameter of tunnel support structure is calculated according to the parameters setting value and tunnel model of tunnel support structure, obtain the construction parameter value of final tunnel support structure, prepare the rack support unit of the prefabricated assembled space net rack supporting construction of every ring, after tunnel excavation, tunnel support close ring is formed in the prefabricated rack support unit of the excavation section quick-assembling completed, the assembly of multi-ring network frame member is completed and carries out gunite concrete again.Structure of the invention is simple, easy to assembly, is not necessarily to gunite concrete, can undertake whole tunnel loads by grid structure itself, improve construction efficiency.

Description

Prefabricated assembly type space grid structure for tunnel support and construction method thereof
Technical Field
The invention belongs to the technical field of tunnel engineering construction, and particularly relates to a prefabricated assembly type space grid structure for tunnel support and a construction method thereof.
Background
Tunnel engineering construction is complicated changeable because of topography, geological conditions very easily take place different degree disasters, leads to tunnel supporting construction to take place to warp, threatens to tunnel stability to different degrees ground, and serious unable satisfying design lining section requirement influences tunnel safety construction, especially brings very big the degree of difficulty for the tunnel construction that the span is big, the structure is complicated, the deformation requires rigorously. The traditional tunnel primary support structure at present comprises an anchor-shotcrete structure, a grid support, a reinforced concrete support structure and the like, and the existing support structure cannot meet the requirements of the existing support structure on bearing capacity and support time. Taking the most common grid support structure as an example, the grid support structure is formed by combining grid steel frames and profile steel frames, spraying and mixing, anchor rods and reinforcing mesh, wherein the steel frames are in the unit of roof truss, and the longitudinal distance is generally 0.5-1.5 m/roof truss. Due to the longitudinal discreteness of the steel frame and the weak bearing capacity of the grid steel frame, the steel frame has weak capacity of bearing the load of surrounding rocks in the time before the concrete is sprayed, and the next procedure can be carried out after the concrete is sprayed, so that the construction period is prolonged, and the construction efficiency of a supporting structure is reduced.
With the development of the prefabricated assembly technology of the components, the prefabrication and assembly of the supporting structure in the tunnel construction become necessary gradually, and the method is a main measure which can provide engineering quality and construction speed and reduce cost. The construction of tunnel engineering by a shield method is a typical representative of assembled lining support, but the construction cost of the tunnel by the shield method is high, so that the construction of the tunnel by the mining method still accounts for a considerable proportion at present, but the research on the prefabrication and assembly technology of the tunnel support structure by the mining method is less. At present, the most common support system for tunnel support by a mine method is a combined support system consisting of sprayed concrete, anchor rods, steel arch frames and the like, the common steel arch frames have higher support strength and rigidity and can enhance the structural capability of primary support, but the longitudinal connecting steel bars and locking feet of the traditional steel arch frames are connected with steel frames by welding, the construction speed is low, the requirements of early sealing of tunnel construction are not met, the space of field overhead welding operation is narrow, the quality can be ensured, and although the support technology of the steel arch frames is mature, weak axis distortion and instability are easy to occur due to low lateral rigidity. On the premise of meeting safety and reliability, by taking reference to the current tunnel interval shield segment splicing technology, a prefabricated splicing type supporting structure is developed, so that the alternate operation time of all working procedures is shortened, the construction efficiency is improved, and the requirement is very high.
As for the space grid structure, the space grid structure has the characteristic of three-dimensional stress and can bear the action in all directions, the grid structure is generally a high-order hyperstatic structure, if one rod is partially failed, only one hyperstatic time is needed, the internal force can be readjusted, the whole structure is generally not failed, and the space grid structure has higher safety reserve. The integrated anti-seismic load bearing device has the advantages of good integrity, good stability and large space rigidity, can effectively bear asymmetric load, concentrated load and dynamic load, and has better anti-seismic performance. The spatial grid structure is widely applied to roofs of buildings such as gymnasiums, movie theaters, exhibition halls, waiting halls, stadium stand awnings, hangars, bidirectional large-column-distance workshops and the like. However, the number of rods of the space grid structure converged on the node is large, the manufacturing and installation are complex compared with a plane structure, and in addition, the particularity of the tunnel supporting structure, the limitation of the construction space and the limitation of the tunnel supporting structure on the calculation and the requirement of the bearing capacity are not applied to the tunnel construction.
Disclosure of Invention
The invention provides a prefabricated space grid structure suitable for tunnel support and a construction method thereof, aiming at the problems of long construction time and insufficient bearing capacity of the traditional support type.
The invention provides a prefabricated assembly type space grid structure for tunnel supporting, which is characterized in that: the prefabricated space net rack supporting structure comprises at least two prefabricated net rack supporting members, connecting members connected with adjacent net rack supporting members are respectively arranged at two ends of each net rack supporting member, and the at least two net rack supporting members are connected end to end through the connecting members to form a closed supporting structure with the same section as the section shape of a supporting tunnel; each net rack supporting component is a grid supporting structure consisting of an upper chord member, a lower chord member and a web member, the upper chord member forms an earth facing net surface of the net rack supporting component contacting with the inner wall of the tunnel, the lower chord member forms an earth backing net surface of the net rack supporting component, the web member is connected between the upper chord member and the lower chord member and is separated between the upper chord member and the lower chord member to form a plurality of grid units, and a metal net is arranged on the earth facing net surface of each net rack supporting component.
The invention has the following excellent technical scheme: the grid unit soil facing surface and the soil backing surface of the net rack supporting component are triangular, square, rectangular, pentagonal or hexagonal, and the vertical surface is triangular.
The invention has the following excellent technical scheme: the net rack supporting component is a grid type supporting frame consisting of a plurality of triangular pyramids or a plurality of rectangular pyramids or a plurality of hexagonal pyramids.
The invention has the following excellent technical scheme: the upper chord member and the lower chord member of the net rack supporting member are arc-shaped rod bodies formed by welding or directly bending or connecting any one or more rod members of steel pipes, section steel, reinforcing steel bars and steel pipe concrete or connecting pieces; and web members are connected between the upper chord member and the lower chord member through welding or connecting pieces to form an arc-shaped grid structure, and the web members are any one or more members selected from steel pipes, section steel, reinforcing steel bars and steel pipe concrete.
The invention has the following excellent technical scheme: the connecting members are mutually matched tenon connecting pieces or sleeve connecting pieces or buckle connecting pieces or plug-in or welding connecting pieces, the mutually matched first connecting pieces and second connecting pieces of each connecting member are respectively arranged at the butt joint parts of two adjacent net rack supporting members, and the connecting members at the two ends of each net rack supporting member are also mutually matched; at least two net rack supporting members are connected into an annular, rectangular, horseshoe-shaped or polygonal closed supporting structure with the cross section the same as that of the supporting tunnel in a splicing or welding or splicing and welding combination mode through a first connecting piece and a second connecting piece.
The invention provides a construction method of a prefabricated space grid structure for tunnel support, which is characterized by comprising at least two rings of prefabricated space grid support structures in any one of claims 1 to 5, and the construction method comprises the following concrete steps:
(1) acquiring various parameter set values and a tunnel model of a tunnel supporting structure; calculating the bearing load of the tunnel supporting structure and the elastic modulus of the equivalent space shell according to the parameter item set value and the tunnel model; taking the bearing load and the elastic modulus as input of a finite element algorithm, calculating an internal force parameter of the tunnel supporting structure, verifying the safety of the tunnel supporting structure according to the internal force parameter to obtain a corresponding verification result, and finally adjusting the value of the parameter item according to the verification result to obtain a final construction parameter value of the tunnel supporting structure;
(2) determining the subsection of each ring of prefabricated assembly type space net rack supporting structure according to the construction parameter values of the tunnel supporting structure calculated in the step (1), and selecting a proper rod piece to manufacture a single net rack supporting member of each ring of prefabricated assembly type space net rack supporting structure and a connecting piece of the net rack supporting member in a factory or on the spot according to the subsection condition;
(3) after a tunnel is excavated, quickly assembling and prefabricating a single net rack supporting member at an excavated section to form a tunnel supporting closed ring, wherein two adjacent net rack supporting members are directly and quickly connected through connecting pieces at the end parts of the net rack supporting members, the connecting pieces comprise tenon connecting pieces or sleeve connecting pieces or buckle connecting pieces or disc buckle connecting pieces or plug connecting pieces which are matched with each other, and the connecting pieces are directly prefabricated according to the net rack supporting members and then welded at the end parts of the net rack supporting members;
(4) continuously excavating the tunnel, assembling a next ring of prefabricated assembly type space net rack supporting structure at an excavation section, and lapping the space net rack supporting structures of two adjacent rings by adopting longitudinal connecting steel bars;
(5) according to the actual conditions of the engineering, after the multi-ring net frame members are assembled, concrete is sprayed or poured to form a supporting structure.
The invention has the following excellent technical scheme: the parameters of the tunnel supporting structure in the step (1) comprise all or any parameters of the longitudinal supporting length of the single prefabricated assembly type space net rack supporting structure, the number of rod bodies in the longitudinal section of the tunnel supporting structure per linear meter, the thickness of primary support, the material thickness of the rod bodies, the diameter of the connecting piece, the circumferential distance of the connecting piece, the materials of the rod pieces and the connecting piece, and the geometric dimensions of the rod pieces and the connecting piece.
The invention has the following excellent technical scheme: the bearing load of the tunnel supporting structure calculated in the step (1) comprises the self-weight load of the tunnel supporting structure and the external load of the tunnel supporting structure;
the self-weight load f of the tunnel supporting structure is calculated by adopting a formula (I):
f＝γ1bh1； ①
in formula (I), gamma1Representing the concrete weight of the tunnel supporting structure, b representing the longitudinal width of the calculation unit, h1Representing the thickness of the tunnel supporting structure;
the external load of the tunnel supporting structure comprises calculation of at least one of stratum resistance borne by the tunnel supporting structure and surrounding rock pressure borne by the tunnel supporting structure; the surrounding rock pressure borne by the tunnel supporting structure comprises surrounding rock vertically-uniformly-distributed pressure and horizontally-uniformly-distributed pressure borne by the tunnel supporting structure;
after the surrounding rock pressure borne by the tunnel supporting structure is calculated, the surrounding rock pressure is adjusted according to a load coefficient, wherein the load coefficient is the ratio of a trial-calculated load value to a maximum load value.
The invention has the following excellent technical scheme: the calculation process of the stratum resistance borne by the tunnel supporting structure is as follows:
(1) calculating a formation resistance coefficient of the tunnel model by adopting a Wenkel assumption algorithm;
(2) and calculating the stratum resistance borne by the tunnel supporting structure according to the stratum resistance coefficient by a chain rod method.
The invention has the following excellent technical scheme:
in the case that the tunnel model is a deep-buried tunnel:
the vertical uniform pressure q of the surrounding rock born by the tunnel supporting structure is calculated by adopting the following formula II,
q＝γ2hq ②
formula II, hqFirst constant x 2S-1w, w ═ a second constant + i (B — a third constant); gamma ray2Indicates the weight of the surrounding rock, hqRepresenting the calculated height of the collapse arch of the surrounding rock, S representing the level of the surrounding rock, wRepresenting a width influence coefficient, B representing a tunnel excavation width, and i representing a surrounding rock pressure increase and decrease rate of each increased unit length;
the horizontal uniform distribution pressure of the surrounding rock borne by the tunnel supporting structure is the product of the calculated vertical uniform distribution pressure q of the surrounding rock borne by the tunnel supporting structure and a specific coefficient; wherein the value of the specific coefficient is related to a surrounding rock level.
The invention has the following excellent technical scheme:
in the case that the tunnel model is a shallow tunnel:
the vertical uniform pressure q of the surrounding rock born by the tunnel supporting structure is obtained by calculation by adopting a formula (III),
wherein,
γ2indicates the weight of the surrounding rock, h2Denotes a height of a tunnel top from the ground, lambda denotes a side pressure coefficient, theta denotes a friction angle of both sides of the tunnel top, B denotes a tunnel excavation width, beta denotes a burst angle at the time of maximum thrust,representing the calculated friction angle of the surrounding rock;
surrounding rock horizontal uniform distribution pressure e borne by tunnel supporting structureiIs obtained by calculation by adopting a formula (IV),
ei＝γ2hiλ ④
wherein, γ2Indicates the weight of the surrounding rock, hiThe distance between any point inside and outside the tunnel and the ground is shown, and the lambda represents the lateral pressure coefficient.
The parameters of the tunnel supporting structure in the step (1) comprise all or any parameters of the longitudinal supporting length of the single-piece prefabricated assembly type space net rack supporting structure, the number of rod bodies in the longitudinal section of the tunnel supporting structure per linear meter, the thickness of primary support, the material thickness of the rod bodies, the diameter of the connecting piece, the circumferential distance of the connecting piece, the materials of the rod pieces and the connecting piece, and the geometric dimensions of the rod pieces and the connecting piece, wherein the connection form of the rod pieces, the material and the geometric dimensions (length, diameter or thickness and the like) of the connecting member
The invention has the beneficial effects that:
(1) the supporting structure of the invention makes full use of the good stress performance of the space grid structure and the rapid assembly type construction convenience, changes the traditional 'line supporting' of a steel arch frame and the like into 'surface supporting', and improves the safety and the stability of the tunnel;
(2) the prefabricated assembly type space net rack supporting structure disclosed by the invention can bear the load of all tunnels by relying on the net rack structure without spraying concrete, is quick to assemble, can spray concrete after a plurality of excavation and assembly cycles, reduces the alternation of construction procedures, improves the construction efficiency, ensures the safety of tunnel construction, and is particularly suitable for tunnel excavation sections with complex geology and strict deformation control;
(3) the space net rack supporting structure is formed by connecting a plurality of arc-shaped supporting structures through the quick assembling joints, the arc-shaped supporting structures can be directly processed in advance or processed on site according to tunnel parameters, and then are quickly assembled to form an integral annular structure, so that the problems of slow construction of tunnels, difficult quality guarantee and the like caused by welding are solved, and the construction efficiency is improved;
(4) the space net rack supporting structure consists of a plurality of pyramid structures, one side of each pyramid structure is planar, the other side of each pyramid structure is dotted, the surfaces are connected with the points through a plurality of pull rods, under the action of node load, each rod piece mainly bears axial tension and pressure, the strength of materials can be fully exerted, a plurality of pyramid parts are regularly combined together, the integrity is good, the stability is good, the space rigidity is high, the asymmetrical load, the concentrated load and the dynamic load can be effectively borne, and the earthquake-resistant performance is good;
(5) according to the invention, in the construction process, the parameters of the net rack supporting structure are calculated and designed aiming at the bearing capacity required by the tunnel before the concrete is sprayed, so that the designed supporting structure can meet the construction safety, the prefabricated supporting structure can provide larger bearing capacity before the concrete is sprayed, the next procedure can be carried out in a certain operation range without spraying the concrete, and the construction efficiency is improved.
(6) The space grid structure combination of the invention is regular, the shapes and the sizes of a large number of nodes and rod pieces are the same, and the rod pieces and the nodes have fewer specifications, thereby being convenient for production and having high product quality.
According to the structure and the construction method, the multi-ring grid frame members can be assembled according to actual conditions, then concrete is sprayed, the supporting members in the structure and the construction method are prefabricated in a factory mode, production is facilitated, quality is controllable, field assembly and construction are convenient, concrete does not need to be sprayed, all tunnel loads can be borne by the grid frame structure, alternating time of all working procedures is greatly shortened, rapid construction of tunnel supporting can be achieved, and construction efficiency is improved.
Drawings
Fig. 1 is a schematic structural view of a prefabricated spatial grid support structure of the present invention;
figure 2 is a schematic view of the structure of the net rack support member of the present invention;
figure 3 is a schematic illustration of the splicing of the net rack support members of the present invention;
FIGS. 4a to 4e are schematic views showing the structure of various connecting members according to the present invention;
figure 5 is a plan view of the net rack support member of the present invention;
figure 6 is a schematic cross-sectional view of a rack support member of the present invention;
figures 7a to 7c are schematic structural views of different grid cells of a rack support member;
fig. 8a to 8c are schematic diagrams of the assembly of the grid cells of fig. 7a to 7c, respectively.
Figure 9 is a schematic view of the rack frame support width and distance;
fig. 10 is a schematic view of the construction state of the present invention.
In the figure: the method comprises the following steps of 1-a net rack supporting component, 2-a tunnel to be supported, 3-an upper chord, 4-a lower chord, 5-a web member, 6-a metal net, 7-a connecting component, 7-1-a first connecting piece, 7-2-a second connecting piece, 8-a concrete lining, a-the width of the net rack supporting component, and b-the distance between two adjacent net rack supporting structures.
Detailed Description
The invention is further illustrated by the following figures and examples. Fig. 1 to 8 are drawings of embodiments, which are drawn in a simplified manner and are only used for the purpose of clearly and concisely illustrating the embodiments of the present invention. The following claims presented in the drawings are specific to embodiments of the invention and are not intended to limit the scope of the claimed invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it is to be understood that the terms "upper", "lower", "inside", "outside", "left", "right", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, or the orientations or positional relationships that the products of the present invention are conventionally placed in use, or the orientations or positional relationships that are conventionally understood by those skilled in the art, and are used for convenience of describing the present invention and simplifying the description, but do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention.
As shown in fig. 1 to 6, the prefabricated spatial grid structure for tunnel supporting provided by the invention specifically includes at least two prefabricated grid support members 1, two ends of each grid support member 1 are respectively provided with a connecting member 7 connected with the adjacent grid support member 1, the connecting members 7 are mutually matched tenon connecting members (as shown in fig. 4a and 4b) or sleeve connecting members or buckle connecting members (as shown in fig. 4c and 4d) or plug connecting members or disc buckle connecting members (as shown in fig. 4e), a first connecting member 7-1 and a second connecting member 7-2, which are mutually matched, of each connecting member 7 are respectively arranged at the butt joint position of the adjacent two grid support members 1, and the connecting members 7 at the two ends of each grid support member 1 are also mutually matched; at least two net rack supporting members 1 are spliced into an annular, rectangular, horseshoe-shaped or polygonal closed supporting structure with the cross section the same as that of the supporting tunnel 2 through a first connecting piece 7-1 and a second connecting piece 7-2. The prefabricated net rack supporting component 1 is prefabricated according to the section shape of the tunnel, is matched with the section shape of the tunnel, and does not limit the specific assembled shape.
Each net rack supporting component 1 in the prefabricated assembly type space net rack supporting structure for tunnel supporting provided by the invention is a grid supporting structure consisting of an upper chord 3, a lower chord 4 and a web member 5, the upper chord 3 forms an earth-facing net surface of the net rack supporting component 1 contacted with the inner wall of a tunnel 6, the lower chord 4 forms a back earth net surface of the net rack supporting component 1, the web member 5 is connected between the upper chord 3 and the lower chord 4, a plurality of grid units are formed between the upper chord 3 and the lower chord 4 in a separated manner, and a metal net 6 is arranged on the earth-facing net surface of each net rack supporting component 1. The soil facing net surface and the soil backing net surface of the net rack supporting component 1 respectively form an outer ring structure and an inner ring structure of the whole support, and the rod bodies on the outer ring structure and the inner ring structure are uniformly arranged, so that the uniform stress on the outer ring structure and the inner ring structure can be ensured.
The soil facing surface and the soil backing surface of the grid unit of the net rack supporting member 1 are triangular, square, rectangular, pentagonal or hexagonal, the vertical surfaces of the grid unit are triangular, the minimum shape unit formed by the rod pieces in the soil facing net surface and the soil backing net surface through the web members 5 is ensured to be triangular, and the supporting strength of the prefabricated member can be further improved through a triangular stable structure. The upper chord 3 and the lower chord 4 of the net rack supporting member 1 are arc-shaped rod bodies formed by welding, directly bending or connecting any one or more of steel pipes, section steel, reinforcing steel bars and steel pipe concrete through connecting pieces; and the web members 5 are connected between the upper chord member 3 and the lower chord member 4 through welding or connecting pieces to form an arc-shaped grid structure, and the web members 5 are any one or more members selected from steel pipes, section steel, reinforcing steel bars and steel pipe concrete.
The net rack supporting component 1 provided by the invention is a grid type supporting frame consisting of a plurality of triangular pyramids or a plurality of rectangular pyramids or a plurality of hexagonal pyramids, the triangular pyramids are shown in figures 7a and 8a, the triangular bottom surfaces of two adjacent triangular pyramids are connected into a curved surface, the curved surface is the soil facing surface of the net rack supporting component 1, three supporting rods forming the triangular bottom surfaces of the triangular pyramids are upper chords of the net rack supporting component 1, the conical tips of two adjacent triangular pyramids are connected into a whole through the inner chords 4, and the three supporting rods forming the triangular pyramid are web members of the net rack supporting component 1 after being connected. As shown in fig. 7b and 8b, the rectangular pyramids are the same as the triangular pyramids, the bottom surfaces of the rectangular pyramids are connected to form a curved surface, the plane is the soil-facing surface of the net rack support member 1, four support rods forming the bottom surfaces of the four corners of the rectangular pyramids, namely, upper chords of the net rack support member 1, the conical tips of two adjacent rectangular pyramids are connected into a whole through the inner chords 4, and the four support rods forming the rectangular pyramids after connection, namely, web members of the net rack support member 1. As shown in fig. 7c and 8c, the hexagonal bottom surfaces of the hexagonal pyramids are connected to form a curved surface, the curved surface is the soil-facing surface of the net rack support member 1, the six support rods forming the hexagonal bottom surface of the hexagonal pyramid are the upper chords of the net rack support member 1, the cone tips of two adjacent hexagonal pyramids are connected into a whole through the inner chords 4, and the six support rods forming the hexagonal pyramid are the web members of the net rack support member 1 after being connected.
The following further describes the present invention with reference to the embodiments, and the parameter value determination scheme in the embodiments of the present invention may be implemented by using various computer languages, for example, object-oriented programming language Java and transliterated scripting language JavaScript.
The embodiment provides a construction method of a prefabricated assembled space grid structure for tunnel supporting, which mainly aims at a grid type supporting frame formed by a plurality of rectangular pyramids of a grid type supporting member 1, the distance b between two adjacent ring grid supporting structures can be 0 according to actual conditions, as shown in figure 1, the perimeter of the cross section of a tunnel isWherein n is the number of segments of the tunnel section member, Li is the length of the i-th section member, the connecting member 7 on the net rack supporting member 1 is a joggle connecting piece which can be spliced with each other, and the concrete construction steps of the supporting structure are as follows:
(1) determining the construction parameter value of the tunnel supporting structure:
a. acquiring various parameter set values and a tunnel model of a tunnel supporting structure; the parameter items include but are not limited to: the longitudinal support length of each space net rack support structure, the number (single side) of reinforcing steel bars (pipes) on the longitudinal section of each linear meter of space net rack support structure, the thickness of primary support, the material thickness (such as the diameter of the reinforcing steel bars and the wall thickness of the steel pipes) of rod bodies, the diameter of connecting pieces, the circumferential distance of the connecting pieces and the like. The set values of these parameters may be empirical values or design values. The tunnel model of the embodiment of the invention is used for simulating the actual tunnel condition, and is related to tunnel engineering geology, hydrogeology conditions, the design and construction experience of the existing tunnel and the like, and the tunnel condition is related to parameters such as surrounding rock level, tunnel extension mode, tunnel depth, tunnel section shape and the like at the tunnel;
b. according to the set value of the parameter item and the tunnel model, calculating the bearing load of the tunnel supporting structure and the elastic modulus of the equivalent space shell, wherein the bearing load mainly comprises a dead weight load and an external load, and the external load mainly comprises: formation resistance, surrounding rock pressure, and the like; the tunnel supporting structure can be equivalent to a space shell structure, the elastic modulus of the equivalent space shell is calculated by using the set values of various parameter items of the tunnel supporting structure, the tunnel supporting structure can be better simulated by adopting the method, and the calculated elastic modulus can be equivalent to the integral elastic modulus of the tunnel supporting structure;
c. taking the bearing load and the elastic modulus as the input of a finite element algorithm, and calculating the internal force parameters of the tunnel supporting structure, wherein the internal force parameters comprise: bending moment, axial force (axial force), shear force, and the like; verifying the safety of the tunnel supporting structure according to the internal force parameters to obtain a corresponding verification result, adjusting the values of the parameter items according to the verification result, and if the verification result indicates that the safety requirements are not met, adjusting the values of the parameter items to continue verification to determine the parameter items meeting the safety requirements. If the verification result indicates that the safety requirement is met and the safety requirement is exceeded, the values of the parameter items need to be adjusted to continue verification, so that the materials are saved, and the cost is reduced;
d. finally, according to the verification result, adjusting the values of the parameter items to obtain the final construction parameter values of the tunnel supporting structure;
(2) determining the subsection of each ring of prefabricated assembly type space net rack supporting structure according to the construction parameter values of the tunnel supporting structure calculated in the step (1), selecting proper rods and connecting pieces, and manufacturing a single net rack supporting member of each ring of prefabricated assembly type space net rack supporting structure and the connecting pieces of the net rack supporting members in a factory or on the spot according to the subsection condition;
(3) after a tunnel is excavated, a single net rack support member which is prefabricated by fast assembling at an excavated section is connected to form a tunnel support closed ring, two adjacent net rack support members are connected through a connecting member 7, the connecting member 7 comprises a joggle connecting piece, a sleeve connecting piece, a buckle connecting piece, a disc buckle connecting piece or a plug connecting piece which are matched with each other, when the connecting member is the joggle connecting piece, as shown in fig. 4a and 4b, a first connecting piece 7-1 and a second connecting piece 7-2 which form the connecting member 7 are mutually matched with each other, and when the connecting members are connected, only two parts of the connecting members are directly butted, and the lugs of the two parts are mutually embedded into the grooves of the other part and clamped; when the connecting member is a snap-fit connector, as shown in fig. 4c and 4d, the connecting member includes a first connecting member provided with a bayonet and a second connecting member provided with a lock hole, and the second connecting member is correspondingly inserted into the first connecting member and is locked by a lock catch; when the connecting members are connected by the disc buckle, as shown in fig. 4e, the first connecting member is provided with a disc-type hole, and the second connecting member is locked by the locking block after being clamped; the connecting member 7 in the embodiment is welded at the end part of the net rack supporting member after being directly prefabricated according to the net rack supporting member; when the installation of the net rack supporting component is carried out, the electric multifunctional arch installing machine is adopted to replace the traditional vertical frame trolley, the automatic installation is carried out through the operation means of jacking of the multifunctional arch installing trolley, arm grabbing and the like, the multifunctional arch installing machine is provided with the multifunctional arch installing trolley which is provided with an automatic walking and automatic positioning system, the combination of arm and hanging basket is adopted, the omnibearing movement and the accurate hoisting of the arch are realized by the multifunctional arch trolley, the arch installing construction process is completed, the integral movement is rapid and convenient, the applicability is wide, the omnibearing movement of the arch can be realized, the position of any position is in place, and the whole equipment is controlled by a safe hydraulic and electric control system;
(4) continuously excavating the tunnel, and continuously splicing a next ring of prefabricated assembly type space net rack supporting structure at the excavation section by adopting a multifunctional arch frame mounting machine; the adjacent two ring space net rack supporting structures can be lapped by longitudinal connecting steel bars;
(5) according to the actual situation of the engineering, after a single-ring prefabricated assembly type space net rack supporting structure is completed or a plurality of rings of prefabricated assembly type space net rack supporting structures are completed, spraying or pouring concrete on the net rack supporting structures, and wrapping the prefabricated assembly type space net rack supporting structures to form a lining structure; because the space net rack supporting structure has stronger rigidity, the surrounding rock loose load during construction can be borne, the next procedure can be carried out without spraying concrete immediately, in order to accelerate the excavation progress, the spraying concrete is delayed within a certain distance range from the tunnel face, and the space net rack supporting structure can be only used as a bearing structure of primary support.
In the embodiment of the invention, as shown in fig. 10, at least two spatial grid support structures are needed, the longitudinal support length L of each spatial grid support structure, the number (single side) n of reinforcing steel bars (pipes) in each linear meter of the longitudinal section of the spatial grid support structure, the thickness h of the primary support and other construction parameters are preliminarily formulated, and the parameters can take industrial experience values. And for other parameter items, a set value can be assumed, such as the thickness of the rod body material, so that structural mechanics analysis is carried out, and whether the structural safety coefficient meets the requirement or not is checked. And obtaining the values of the parameter items meeting the safety requirement by trial calculation of the parameter items.
In the above embodiment, the dead weight load and the external load are determined as the bearing load of the tunnel supporting structure, and the calculation process for the bearing load is specifically as follows:
calculation of first, dead weight load
Wherein, according to the setting value of parameter item, the step of calculating tunnel supporting construction's dead weight load includes: calculating the self-weight load f of the tunnel supporting structure by adopting a formula I; the formula (I) is as follows:
f＝γ1bh1；
wherein, γ1Representing the concrete weight of the tunnel supporting structure, b representing the longitudinal width of the calculation unit, h1The thickness of the tunnel supporting structure is shown.
Second, calculation of external load
The method comprises the following steps of calculating the external load of a tunnel supporting structure according to a tunnel model, wherein the steps comprise at least one of the following steps: calculating the stratum resistance borne by the tunnel supporting structure according to the tunnel model; and calculating the surrounding rock pressure born by the tunnel supporting structure according to the type of the tunnel model.
1. Calculation of formation resistance
According to the tunnel model, the step of calculating the stratum resistance born by the tunnel supporting structure comprises the following steps: calculating a formation resistance coefficient of the tunnel model by adopting a Wenkel assumption algorithm; and calculating the stratum resistance borne by the tunnel supporting structure according to the stratum resistance coefficient by a chain rod method. In particular, in the chain link method, formation resistance is simulated with a ground spring. And determining the stratum resistance coefficient according to soil layer conditions, and calculating according to a winker assumption. In the calculation, the spring in tension is eliminated.
2. Calculation of surrounding rock pressure
According to the type of the tunnel model, the step of calculating the surrounding rock pressure born by the tunnel supporting structure comprises the following steps: and respectively calculating the vertical uniform distribution pressure and the horizontal uniform distribution pressure of the surrounding rock borne by the tunnel supporting structure according to the type of the tunnel model. And the calculation modes of the vertically and horizontally uniformly distributed pressure under the tunnel model are different. The tunnel models are different in types, the calculation of the vertically uniformly distributed pressure is different, and the calculation modes of the horizontally uniformly distributed pressure are also different. The calculation of the surrounding rock pressure in the embodiment will be further described in conjunction with the deep-buried tunnel and the shallow-buried tunnel.
2-1, deep buried tunnel condition
The deep-buried tunnel condition refers to a condition in which the distance from the center line, top or bottom of the tunnel to the earth's surface exceeds a certain value, and in the present embodiment refers to a condition other than the shallow-buried tunnel condition. For the calculation of the vertically equispaced pressure: under the condition that the tunnel model is a deep-buried tunnel, calculating the vertical uniform distribution pressure q (unit can be kPa) of surrounding rocks borne by a tunnel supporting structure by adopting a formula II; wherein, the formula II is:
q＝γ2hq
wherein h isqFirst constant x 2S-1w, w ═ a second constant + i (B — a third constant);
wherein, γ2Representing the weight of the surrounding rock (the unit can be kN/m)3)，hqThe calculated height of the collapse arch of the surrounding rock is expressed (the unit can be m), S represents the surrounding rock level, w represents the width influence coefficient, B represents the excavation width of the tunnel (the unit can be m), and i represents the pressure increasing and decreasing rate of the surrounding rock per unit increasing length.
Alternatively, the first constant may be 0.45, the second constant may be 1, and the third constant may be 5. Accordingly, hq＝0.45×2S-1w, w ═ 1+ i (B-5). Wherein, when B is less than 5m, i is 0.2, and when B is more than or equal to 5m, i is 0.1.
For horizontal profiling pressure calculation: and under the condition that the tunnel model is a deep-buried tunnel, determining the product of the vertical uniform distribution pressure of the surrounding rock borne by the tunnel supporting structure and a specific coefficient as the horizontal uniform distribution pressure of the surrounding rock borne by the tunnel supporting structure, wherein the value of the specific coefficient is related to the surrounding rock level. For example, the horizontal distribution pressure in this case can be determined by the following table 1:
TABLE 1
Grade of surrounding rock Ⅰ～Ⅱ Ⅲ Ⅳ Ⅴ
Horizontal uniform pressure 0 <0.15q (0.15～0.30)q (0.30～0.50)q
2-2, deep buried tunnel condition
Shallow tunnel refers to the situation that the distance between the center line, top or bottom of the tunnel and the ground surface is lower than a certain value, for example, the buried depth of the tunnel is more than hqAnd less than 2.5hqThe case (1).
For the calculation of the vertically equispaced pressure: under the condition that the tunnel model is a shallow tunnel, calculating surrounding rock vertically uniform distribution pressure q borne by a tunnel supporting structure by adopting a formula III; wherein, the formula (c) is:
wherein,
γ2representing the weight of the surrounding rock (the unit can be kN/m)3)，h2The height of the top of the tunnel from the ground (in m), lambda represents the lateral pressure coefficient, theta represents the friction angle (in m) on both sides of the top of the tunnel, and is generally taken as an empirical value, B represents the tunnel excavation width or tunnel span (in m),beta represents the angle of rupture at maximum thrust (which may be in units),indicating that the surrounding rock calculates the friction angle (which may be in °).
Alternatively, the fourth constant may be 1, the fifth constant may be 1, and the sixth constant may be 1. Accordingly, the number of the first and second electrodes,
calculation for horizontal profiling pressure: under the condition that the tunnel model is a shallow tunnel, calculating the horizontal uniform distribution pressure e of the surrounding rock born by the tunnel supporting structure by adopting a fourth formulai(ii) a Wherein, the formula (iv) is:
ei＝γ2hiλ
wherein, γ2Representing the weight of the surrounding rock (the unit can be kN/m)3)，hiThe distance (unit can be m) between any point inside and outside the tunnel and the ground, and lambda represents the lateral pressure coefficient.
Further, the surrounding rock pressure obtained through calculation is the maximum loose load borne by the tunnel lining, but a certain space effect exists in consideration of the supporting effect of the surrounding rock in front of the tunnel face and the supporting effect of the primary support and the secondary lining in the rear, and the space net rack supporting structure cannot bear the large load in the actual construction process, so that the load is reduced in the design. Specifically, after the surrounding rock pressure is calculated, the surrounding rock pressure is adjusted according to a load coefficient, wherein the load coefficient is the ratio of the trial-calculated load value to the maximum load value. For example, let q be the surrounding rock load q, where μ represents the load factor, and q' represents the relaxation load acting on the tunnel support structure (space grid support structure) as the ratio of the passing load value to the maximum load value through trial calculation.
It is worth pointing out that in the stage of erecting the space net rack supporting structure and the stage of spraying concrete, the load acting on the tunnel supporting structure is adjusted by adopting different load coefficients mu, so as to obtain the load according with the actual stress condition of the supporting structure.
The calculation method of the bearing load under different scenes is introduced above, and an example of calculating the elastic modulus of the tunnel supporting structure in step 1 will be further described with reference to an application scene.
Specifically, taking the horseshoe-shaped cross-section structural lining of the underground tunnel shown in fig. 1 as an example, the structural stress mode is mainly eccentric compression, and the supporting structure in the stage of erecting the supporting structure and the stage of spraying concrete is equivalent to a space shell structure with a certain thickness according to the principle of equivalent tension-compression rigidity.
In the stage of erecting the supporting structure, EA is equal to Eg(Ag+A‘g) And a ═ Lh, accordingly, step 13 comprises: calculating the elastic modulus E of the equivalent space shell of the tunnel supporting structure by adopting a formula fifth; wherein, the formula is:
wherein A isg、A‘gThe cross-sectional area (unit can be m) of the rod body in the tension and compression area2)，EgThe material modulus of the rod body is represented, L represents the longitudinal length of one wire frame supporting structure in the tunnel supporting structure, and h represents the thickness of the equivalent space shell.
Wherein, under the condition that the rod body is a steel bar,wherein n represents the number of rod bodies contained in the longitudinal section of a linear meter net rack supporting structure, and D represents the diameter of the reinforcing steel bar.
In the case where the rod body is a steel pipe,n represents the number of rod bodies contained in the longitudinal section of the linear meter net rack supporting structure, D represents the diameter of the steel pipe, and t represents the wall thickness of the steel pipe.
The calculation of the elastic modulus in the steel frame erecting stage is introduced, and for the concrete spraying stage, according to the existing design experience, the contribution of the rigidity of steel to the equivalent rigidity of the section can be almost ignored in the stage. Therefore, the rigidity of the sprayed concrete can be directly adopted as the rigidity of the equivalent section at the stage.
The calculation of the internal force parameters is realized based on the calculation results of the bearing load and the elastic modulus of the equivalent space shell, and the problem of solving the internal force of the tunnel section can be simplified into a plane strain problem according to the basic principle of elasticity mechanics. And (3) calculating the internal forces (bending moment M, axial force N and shearing force Q) of the supporting structure in the steel frame erecting stage and the concrete spraying stage respectively by adopting a finite element method.
After the internal force parameters are obtained, the safety of the tunnel supporting structure can be verified based on the internal force parameters. The following embodiment of the invention verifies the safety by combining different construction stages to obtain a proper design value of the structural parameter.
In the stage of erecting the space net rack supporting structure, calculating a corresponding verification result by adopting a formula (sixth); and when the verification result is that the safety factor is greater than or equal to the first value, determining that the safety of the tunnel supporting structure meets the requirement. Assuming that the first value is 2.4, when K is greater than or equal to 2.4, the values of the parameter items of the tunnel supporting structure meet the safety requirement; otherwise, step 16 is executed to adjust the values of the parameter items, and the next trial calculation is performed until a proper value is obtained.
Wherein the formula is: KN ═ α RgA, where K represents a safety factor, N represents an axial force, α represents an eccentricity influence coefficient of the axial force, and RgThe ultimate tensile strength of the material of the rack support structure is shown, and a represents the cross-sectional area of the equivalent space casing.
Optionally, the eccentricity of the shaft force and the eccentricity and equivalent space envelope of the shaft forceThe thickness of the body is relevant. For example,wherein e is0Represents the axial force eccentricity and h represents the thickness of the equivalent space housing.
The step of obtaining the verification result may further include a step of calculating other parameter item values, and specifically, according to the internal force parameter, verifying the safety of the tunnel supporting structure to obtain a corresponding verification result. Then, calculating the structural parameters of the connecting piece by adopting a formula; wherein, formula (c) is:
k represents the safety factor, Q represents the shear force, RgRepresenting the ultimate tensile strength of the material of the grid support structure, AkIndicating the cross-sectional area of the joint of the connecting member and the rod bodyeThe length of the selected beam unit in the finite element algorithm is shown, theta represents the friction angle of two sides of the top of the tunnel, and c represents the circumferential distance of the connecting piece. Alternatively, the seventh constant may be 0.8, and, accordingly,
therefore, through the calculation of the shear strength, the diameter d and the annular distance c of the connecting piece can meet the requirement of the shear strength of the structure.
The safety verification method in the stage of erecting the space grid support structure is described above, and the safety verification method after the stage of spraying concrete is further described below.
After the stage of spraying concrete, under the condition that the height of the concrete compression area is less than or equal to a threshold value, calculating a corresponding verification result by adopting a formula (I); and when the verification result is that the safety factor is greater than or equal to the first value, determining that the safety of the tunnel supporting structure meets the requirement.
Wherein the first formula (b) is:
KNe≤Rwbx(h0-x/2)+RgA‘g(h0-a’)
wherein,
k represents a safety factor, N represents an axial force, e’Indicating the distance, R, from the center of gravity of the rod body in the tension and compression zones to the point of application of the axial forcewThe bending compressive ultimate strength of the concrete is expressed, b represents the longitudinal width of a calculation unit, x represents the height (the unit can be m) of a compression area of the concrete, and RgRepresenting the ultimate tensile strength of the material of the grid support structure, Ag、A‘gRepresenting the cross-sectional area (in m) of the rod body in the tension and compression zones2) And a' represent the closest distance (m) from the center of gravity of the rod body in the tension and compression area to the section edge of the shell in the equivalent space, and h0Represents the effective height, h, of the cross section of the equivalent space casing0＝h-a。
In particular, in the stressed phase after the concrete-spraying phase, there is R moment taken on the action point of the shaft forceg(Age-A‘ge’)＝Rwbx(e-h0-x/2), from which can be derived: wherein R iswRepresenting the ultimate bending compressive strength of the concrete, x representing the height of the compression zone of the concrete, Rg，R‘gRepresenting calculated strengths of tension, compression, of material of the supporting structure of the grid, Ag、A‘gShowing the cross-sectional area of the rod in the tension and compression zone, e 'showing the distance from the center of gravity of the rod in the tension and compression zone to the point of application of axial force, a' showing Ag、A‘gThe closest distance h from the center of gravity of the shell to the edge of the section of the equivalent space0Representing the effective height of the cross section of the equivalent spatial shell.
Accordingly, assume a threshold of 0.55h0Then when x is less than or equal to 0.55h0When the pressure is large, the pressure is calculated according to an eighth formula, namely R is greater than or equal to KNewbx(h0-x/2)+RgA‘g(h0A '), calculating to satisfy x ≧ 2 a', if not, x<2 a', according to the proportion of R is more than or equal to KNegAg(h0-a') calculation.
After the stage of spraying concrete, under the condition that the height of the concrete compression area is greater than a threshold value, adopting a formula ninthly, and calculating a corresponding verification result; and when the verification result is that the safety factor is greater than or equal to the first value, determining that the safety of the tunnel supporting structure meets the requirement. Wherein, the formula ninthly is:wherein K represents factor of safety, N represents the axial force, e represents the distance from the center of gravity of the rod body to the point of action of the axial force, RaRepresenting the ultimate compressive strength of the concrete, b representing the longitudinal width of the calculation unit, RgA 'representing the ultimate tensile strength of the material of the net frame supporting structure'gThe sectional area of the rod body is shown, a' represents the closest distance from the center of gravity of the rod body to the sectional edge of the equivalent space shell, and h0Representing the effective height of the cross section of the equivalent spatial shell.
Accordingly, assume a threshold of 0.55h0Then when x is greater than 0.55h0In the case of a small eccentric compression member, the sectional strength is calculated according to the ninth formula, and the eighth constant may be 0.5, that is
The calculation mode of the main reinforcement in the construction stage is introduced above, and the safety factor after reinforcement is further introduced below:
in the present embodiment, it is assumed that the first value is 2.4, that is, when K is greater than or equal to 2.4, the design values of the parameter items indicating the tunnel supporting structure satisfy the safety requirements.
The above is mainly designed and verified for the values of the parameter items of the rod bodies in the tunnel supporting structure, and the values of the parameter items of the connecting pieces are further designed and verified with the examples.
Specifically, after the step of verifying the safety of the tunnel supporting structure according to the internal force parameter and obtaining a corresponding verification result, the method further includes: calculating the structural parameters of the connecting piece by adopting a formula (r); wherein formula r is:
k represents the safety factor, Q represents the shear force, RaRepresenting the compressive ultimate strength of the concrete, b representing the longitudinal width of the calculation unit, h0Representing the effective height, R, of the cross-section of the equivalent space envelopegRepresenting the ultimate tensile strength of the material of the grid support structure, AkIndicating the cross-sectional area of the joint of the connecting member and the rod bodyeThe length of the selected beam unit in the finite element algorithm is shown, theta represents the friction angle of two sides of the top of the tunnel, and c represents the circumferential distance of the connecting piece. Assuming that the ninth constant is 0.07 and the tenth constant is 0.8, accordingly, the tenth formula is:according to the formula, the limit value of the circumferential distance of the connecting piece meeting the shearing resistance requirement can be calculated.
In the embodiment of the invention, when the safety factor is smaller than the safety requirement threshold value as a verification result, the value of the parameter item is increased; when the verification result shows that the safety coefficient exceeds the safety requirement threshold value and reaches a specific value, reducing the value of the parameter item; and when the verification result shows that the safety coefficient exceeds the safety requirement threshold and does not reach the specific value, keeping the set value of the parameter item unchanged. Taking the safety factor K as an example, assuming that the first value is 2.4, if K is less than 2.4, indicating that the current design value of the parameter item of the tunnel supporting structure is unsafe, increasing the design value, and recalculating; if K >2.4, the bearing capacity of the tunnel supporting structure is more abundant, the design value of the parameter item needs to be reduced, and recalculation is carried out; when K is slightly larger than 2.4, the bearing capacity of the tunnel supporting structure can meet the requirement, and the tunnel supporting structure is economical.
It is worth pointing out that the primary support is used as a temporary structure in the construction period and bears the proportional coefficient of the surrounding rock load, and after the secondary lining is constructed, the stress of the primary support is improved, so that the crack width detection is not needed in the construction period, but the primary support can be used as a reference index in the design process. Reinforced concrete tension, bending and eccentric compression members, pair e0≤0.55h0The eccentric pressing member of (2) can be used without detecting the width of the crack. Otherwise the crack width was calculated as follows:
wherein, ω ismaxRepresents the maximum crack width (which may be in mm); alpha represents the stress characteristic coefficient of a member of the tunnel supporting structure, the tunnel is an eccentric compression member, and alpha can be 1.9;indicating the coefficient of non-uniformity of strain of the longitudinal tension steel bar among the cracks,when in useWhen the temperature of the water is higher than the set temperature,taken at 0.2, whenWhen the temperature of the water is higher than the set temperature,taken at 0.2, whenWhen the temperature of the water is higher than the set temperature,taking 1.0, for a component directly subjected to repeated loads,taking 1.0; rhoteRepresenting the longitudinal reinforcing bar distribution ratio, rho, calculated as the effective area of the tensioned concretete＝As/AceWhen rhote<At 0.01, ρteTaking 0.01; a. thesShowing the section area of the longitudinal ribs in the tension area; a. theceRepresents the effective tensile concrete cross-sectional area, Ace＝0.5bh；CsMeans the distance (unit can be mm) from the outer edge of the outermost layer longitudinally pulled by kilogram to the bottom edge of the pulled area when Cs<At 20 th hour, CsTaking 20 when Cs>At 65, CsTaking 65; d represents the diameter of the steel bar (the unit can be mm), and when the steel bars with different diameters are adopted, d is 4AsV (γ μ), μ represents the sum of the circumferences of the sections of the longitudinal tension bars; gamma represents the surface characteristic coefficient of the longitudinal tension steel bar, the deformed steel bar is 1, and the plain steel bar is 0.7; esRepresenting the modulus of elasticity (in MPa) of the bar; sigmasRepresenting the stress (in MPa) of a longitudinally tensioned bar, σs＝Ns(e-z)/(Asz)，NsRepresenting the value of the axial force calculated for the combination of loads, z representing the distance from the resultant point of tension kg to the resultant point of the compression zone, z being [ 0.87-0.12 (h)0/e)2]h0And z is<0.87h0。
Before the space grid support structure is constructed, the stress condition of the support structure can be calculated according to the geological condition of the tunnel through the calculation process, various parameters of the tunnel support structure are determined by combining the assembling capacity of the assembling trolley and the size of the section of the tunnel, then the support structure with the same shape as the section of the tunnel is prefabricated and assembled, the parameter design of the support structure with larger bearing capacity before concrete spraying is realized, the designed support structure can meet the construction safety, the support structure can provide larger bearing capacity before concrete spraying, the next procedure can be carried out without concrete spraying in a certain operation range, and the construction efficiency is improved.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims (11)

1. The utility model provides a prefabricated assembled space grid structure for tunnel supporting which characterized in that: the prefabricated space net rack supporting structure comprises at least two prefabricated net rack supporting members (1), connecting members (7) connected with adjacent net rack supporting members (1) are respectively arranged at two ends of each net rack supporting member (1), and the at least two net rack supporting members (1) are connected end to end through the connecting members (7) to form a closed supporting structure with the same section as the section of a supporting tunnel (2); each net rack supporting component (1) is a grid supporting structure consisting of an upper chord (3), a lower chord (4) and a web member (5), the upper chord (3) forms an earth-facing net surface of the net rack supporting component (1) contacted with the inner wall of the tunnel (6), the lower chord (4) forms an earth-backing net surface of the net rack supporting component (1), the web member (5) is connected between the upper chord (3) and the lower chord (4) and is separated between the upper chord (3) and the lower chord (4) to form a plurality of grid units, and a metal net (6) is arranged on the earth-facing net surface of each net rack supporting component (1).
2. A prefabricated spatial grid structure for tunnel bracing according to claim 1, wherein: the grid unit soil facing surface and the soil backing surface of the net rack supporting member (1) are triangular, square, rectangular, pentagonal or hexagonal, and the vertical surface is triangular.
3. A prefabricated spatial grid structure for tunnel bracing according to claim 1, wherein: the net rack supporting component (1) is a grid type supporting frame consisting of a plurality of triangular pyramids or a plurality of rectangular pyramids or a plurality of hexagonal pyramids.
4. A prefabricated spatial grid structure for tunnel bracing according to claim 1, wherein: the upper chord (3) and the lower chord (4) of the net rack supporting member (1) are arc-shaped rod bodies formed by welding or directly bending or connecting any one or more of steel pipes, section steel, steel bars and steel pipe concrete or by connecting pieces; and the upper chord member (3) and the lower chord member (4) are connected with the web members (5) through welding or connecting pieces to form an arc-shaped grid structure, and the web members (5) are any one or more of steel pipes, section steel, reinforcing steel bars and steel pipe concrete.
5. A prefabricated spatial grid structure for tunnel bracing according to claim 1, wherein: the connecting members (7) are mutually matched tenon connecting pieces or sleeve connecting pieces or buckle connecting pieces or plug-in or welding connecting pieces, a first connecting piece (7-1) and a second connecting piece (7-2) which are mutually matched with each connecting member (7) are respectively arranged at the butt joint part of two adjacent net rack supporting members (1), and the connecting members (7) at the two ends of each net rack supporting member (1) are also mutually matched; at least two net rack supporting members (1) are connected into an annular, rectangular, horseshoe-shaped or polygonal closed supporting structure with the same cross section as that of the supporting tunnel (2) by adopting a splicing or welding mode or a splicing and welding combined mode through a first connecting piece (7-1) and a second connecting piece (7-2).
6. A construction method of a prefabricated space grid structure for tunnel supporting, wherein the prefabricated space grid structure of any one of claims 1 to 5 comprises at least two rings, and the construction method comprises the following concrete steps:
(1) acquiring various parameter set values and a tunnel model of a tunnel supporting structure; calculating the bearing load of the tunnel supporting structure and the elastic modulus of the equivalent space shell according to the parameter item set value and the tunnel model; taking the bearing load and the elastic modulus as input of a finite element algorithm, calculating an internal force parameter of the tunnel supporting structure, verifying the safety of the tunnel supporting structure according to the internal force parameter to obtain a corresponding verification result, and finally adjusting the value of the parameter item according to the verification result to obtain a final construction parameter value of the tunnel supporting structure;
(2) determining the subsection of each ring of prefabricated assembly type space net rack supporting structure according to the construction parameter values of the tunnel supporting structure calculated in the step (1), and selecting a proper rod piece to manufacture a single net rack supporting member of each ring of prefabricated assembly type space net rack supporting structure and a connecting piece of the net rack supporting member in a factory or on the spot according to the subsection condition;
(3) after the tunnel is excavated, quickly assembling prefabricated single-block net rack supporting members at the finished excavation section to form a tunnel supporting closed ring;
(4) continuously excavating the tunnel, and assembling a next ring of prefabricated assembly type space net rack supporting structure at an excavation section;
(5) according to the actual situation of the engineering, after the single-ring prefabricated assembly type space net rack supporting structure is completed or a plurality of rings of prefabricated assembly type space net rack supporting structures are completed, concrete is sprayed or poured on the net rack supporting structures, and the prefabricated assembly type space net rack supporting structures are wrapped to form a lining structure.
7. The construction method of the prefabricated spatial grid structure for tunnel support according to claim 6, wherein: the parameters of the tunnel supporting structure in the step (1) comprise all or any parameters of the longitudinal supporting length of the single prefabricated assembly type space net rack supporting structure, the number of rod bodies in the longitudinal section of the tunnel supporting structure per linear meter, the thickness of primary support, the material thickness of the rod bodies, the diameter of the connecting piece, the circumferential distance of the connecting piece, the materials of the rod pieces and the connecting piece, and the geometric dimensions of the rod pieces and the connecting piece.
8. The construction method of a prefabricated spatial grid structure for tunnel supporting according to claim 6, wherein the bearing load of the tunnel supporting structure calculated in the step (1) includes a self-weight load of the tunnel supporting structure and an external load of the tunnel supporting structure;
wherein the dead weight f of the tunnel supporting structure is calculated by adopting a formula I
f＝γ1bh1； ①
In formula (I), gamma1Representing the concrete weight of the tunnel supporting structure, b representing the longitudinal width of the calculation unit, h1Representing the thickness of the tunnel supporting structure;
the external load of the tunnel supporting structure comprises calculation of at least one of stratum resistance borne by the tunnel supporting structure and surrounding rock pressure borne by the tunnel supporting structure; the surrounding rock pressure borne by the tunnel supporting structure comprises surrounding rock vertically-uniformly-distributed pressure and horizontally-uniformly-distributed pressure borne by the tunnel supporting structure;
after the surrounding rock pressure borne by the tunnel supporting structure is calculated, the surrounding rock pressure is adjusted according to a load coefficient, wherein the load coefficient is the ratio of a trial-calculated load value to a maximum load value.
9. The construction method of the prefabricated spatial grid structure for tunnel supporting according to claim 8, wherein the resistance of the tunnel supporting structure to the ground layer is calculated as follows:
(1) calculating a formation resistance coefficient of the tunnel model by adopting a Wenkel assumption algorithm;
(2) and calculating the stratum resistance borne by the tunnel supporting structure according to the stratum resistance coefficient by a chain rod method.
10. The construction method of a prefabricated spatial grid structure for tunnel bracing according to claim 8, wherein in case that the tunnel model is a deep-buried tunnel:
the vertical uniform pressure q of the surrounding rock born by the tunnel supporting structure is calculated by adopting the following formula II,
q＝γ2hq ②
formula II, hqFirst constant x 2S-1w, w ═ a second constant + i (B — a third constant); gamma ray2Indicates the weight of the surrounding rock, hqThe calculation height of the collapse arch of the surrounding rock is represented, S represents the surrounding rock level, w represents the width influence coefficient, B represents the tunnel excavation width, and i represents the surrounding rock pressure increase and decrease rate of each increased unit length;
the horizontal uniform distribution pressure of the surrounding rock borne by the tunnel supporting structure is the product of the calculated vertical uniform distribution pressure q of the surrounding rock borne by the tunnel supporting structure and a specific coefficient; wherein the value of the specific coefficient is related to a surrounding rock level.
11. The construction method of a prefabricated spatial grid structure for tunnel bracing according to claim 8, wherein in case that the tunnel model is a shallow tunnel:
the vertical uniform pressure q of the surrounding rock born by the tunnel supporting structure is obtained by calculation by adopting a formula (III),
wherein,
γ2indicates the weight of the surrounding rock, h2Indicating the height of the tunnel roof from the ground, λ the lateral pressure coefficient, θ the tunnel roofThe friction angle at both sides, B represents the tunnel excavation width, β represents the breakout angle at maximum thrust,representing the calculated friction angle of the surrounding rock;
surrounding rock horizontal uniform distribution pressure e borne by tunnel supporting structureiIs obtained by calculation by adopting a formula (IV),
ei＝γ2hiλ ④
wherein, γ2Indicates the weight of the surrounding rock, hiThe distance between any point inside and outside the tunnel and the ground is shown, and the lambda represents the lateral pressure coefficient.
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CN113187519A (en) * 2021-06-01 2021-07-30 重庆大学 Variable prestress supporting method for controlling deformation of tunnel excavation surrounding rock mass
CN113369412A (en) * 2021-06-24 2021-09-10 中铁十一局集团桥梁有限公司 Method, device and equipment for bending steel bar and readable storage medium
CN114880755A (en) * 2022-07-07 2022-08-09 西南交通大学 Surrounding rock grading method, device and equipment for railway tunnel and readable storage medium
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